Drupal 6.6 and Gallery2 2.3 error

Hi all,

I've Gallery2 2.3 installed on a shared host by using Installatron(Direct Admin) and drupal 6.6 installed manually. I have install the Gallery module follow the instruction. there is some warning message during the installation of gallery2, but I've fix it due to the .htaccess file location. I can see the embedded gallery2 UI inside the drupal when click on the "Gallery" link, i can browse through every Gallery2 pages using "admin", but I can't commit any changes. I can't even add album, change setting. Below is the error message it shows up when I tried to commit any changes such as add album, edit group permission and etc.

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Authentication Failure

Your change cannot be completed due to a loss of session data. Please try again. If it still doesn't work, try logging out and logging back in.

Back to the Gallery
Error Detail -
Error (ERROR_REQUEST_FORGED)

* in modules/core/classes/GalleryController.class at line 239 (GalleryCoreApi::error)
* in main.php at line 243 (GalleryController::assertIsGenuineRequest)
* in main.php at line 104
* in modules/core/classes/GalleryEmbed.class at line 189
* in /home/buddyjoy/domains/buddyjoy.com/public_html/sites/all/modules/gallery/gallery_base.inc at line 202 (GalleryEmbed::handleRequest)
* in /home/buddyjoy/domains/buddyjoy.com/public_html/sites/all/modules/gallery/gallery.module at line 452
* in ??? at line 0
* in /home/buddyjoy/domains/buddyjoy.com/public_html/includes/menu.inc at line 348
* in /home/buddyjoy/domains/buddyjoy.com/public_html/index.php at line 18

System Information
Gallery version 2.3
PHP version 5.2.6 apache2handler
Webserver Apache/2
Database mysql 5.0.51a-community
Toolkits Thumbnail, Gd
Operating system Linux ns40.small-dns.com 2.6.18-92.el5 #1 SMP Tue Jun 10 18:51:06 EDT 2008 x86_64
Browser Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4
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Have anyone come across this ? and any solution?

Thanks.
Max Chock.